Apparatus for electrically charging particles suspended in an air current by means of radioactive preparations



May 31, 1960 K. OSWALD APPARATUS FOR EILECTRICALLY CHARGING PARTICLESSUSPENDED IN AN AIR CURRENT BY MEANS OF RADIOACTIVE PREPARATIONS FiledJan. 28. 1957 INVENTOR. Karl 0s HCL/d ATTOYLNEBS United States Patent IAPPARATUS on T ALLY CHARGING PARTICLES SUSPENDED IN AN AIR CURRENT BYMEANS OF RADIOACTIVE PREPARATIONS KarlDswald, Sarnen, Switzerland,assignor to G. A. Messen-Jasc'hin, Sarnen, Switzerland, a firm FiledJan. 28,1957, so. No. 636,754 Claims priority, application SwitzerlandJan. 27, 1956 2 Claims. (Cl. 250- 44 Ihe inventioii relates to anapparatus for electrically charging suspended matter, floating in an aircurrent, with ions of the same polarity by using one or more radioactivepreparations together with an electric field, in order to produceoptimum loading conditions. Such an apparatus has atleast oneradioactive preparation, which is air'an'ged on an electricallyconductive support and the ray-emitting layer of which is remote fromthe air current, a potential difference being produced between theconductive support of the preparation, impressed with a voltage by meansof a direct current source, and at least one counter-electrode, which isarranged outside of the range of the ionizing rays and the effectivecone of rays.

It has been found that the electric field produced by means of theconductive support of the preparation and the counter-electrode exerts acertain separating effect upon already charged particles suspended inthe air current, that means that particles, charged with a polarityopposite to the polarity of the conductive support of the preparationcan be deposited on the preparation. Not only in case of liquid but alsoin case of solid particles, e.g. water or dust, such a deposit providedon the preparation, which suitably is an aor B-ray source, can lead to alowering of the preparation radiation owing to absorption andaccordingly to a substantial decrease in the total amount of producedions.

It is an object of the present invention to provide an apparatus of thedescribed kind, in which the above mentioned drawback is avoided. Forthis purpose the charging apparatus according to the invention comprisesa ring electrode, which is provided immediately downstream of thepreparation and surrounds the ray cone of said preparation, an initialpotential being applied to the ring electrode relatively to theconductive support of the preparation, in order to protect thepreparation against soilure by deposited particles.

Actual practice has shown that the formation of deposits on thepreparation can be perfectly avoided by the arrangement of such a ringelectrode. The ionizing rays will by no means be weakened through thering electrode surrounding the cone of rays, while the conditions of theelectric field will change only to a slight extent, but in no way in adetrimental manner.

The present invention will now be described more fully with reference tothe accompanying schematic drawing illustrating, by way of example, apreferred embodiment of the invention, and in which a longitudinalsectional view of the charging apparatus is shown.

The apparatus shown has a cylindrical housing, which is formed by afirst metallic pipe member 1 and a second pipe member 2, which is madeof insulating material and connected flush with the first member. Whenthe apparatus is in operation, an air current passes through the housing1, 2 in the direction of the arrows indicated. The pipe member 2 ofinsulating material is directly followed by the electrode system of anelectrostatic separator, which system is formed by cylindrical metaltubes 3 and 4, coaxially nested into each other.

2,939,006 Patented May 31, 1960 Within the metal pipe member 1 anionizing cartridge is arranged coaxially to said member. This cartridgecomprises a metallic supporting plate 5, upon the downstream-directedsurface of which an ocor ,B-ray source 6 is arranged, for instance aradium foil. The radiation cone of the preparation 6, limited by theBraggs zone in downstream direction, is designated by a. The conductivesupporting plate 5 carrying the preparation 6 is surrounded by anenclosure 7, which is open in downstream direction and made ofinsulating material. A perforated electrode 8 arranged in upstreamdirection of the preparation 6 projects through the cross-sectional areaof flow, remaining between the pipe member 1 and the ionizing cartridge5-7. The downstream terminal of the insulating pipe member is formed bya perforated counter-electrode 9, which at the same time represents theconductive connection for the electrodes 3 of the separator. Moreover,immediately downstream of the preparation 6, .a ring electrode 10arranged coaxially to the tube axis is provided. The dimensions of thisring electrode 10 are chosen such that it completely surrounds theradiation cone a of the preparation 6.

In the example shown, the counter-electrode 9 is earthed while apotential differing from zero is applied to the other counter-electrode8 by means of a direct current source. On the other hand, a potential isapplied to both, the conductive preparation carrier 5 and the ringelectrode 10, by means of the direct current source, so that, on the onehand, both members 5 and 10 have a higher voltage than thecounter-electrode 8 and, on the other hand, the voltage of the ringelectrode 10 is also higher than the voltage of the preparation carrier5. In a practical example of embodiment, the voltage of thecounter-electrode may amount to 800 v., the voltage of the preparationcarrier 5 may be 2200 v., and the voltage of the ring electrode 10 mayamount to 2500 v.

In practice, the described arrangement of the electrodes and the field,provided by said electrodes and superposed to the radioactivelyirradiated space, has shown to produce a great excess of ions having thesign or polarity of the conductive preparation carrier 5, and mainly inthose space portions situated downstream, which are of greatestimportance for the final charge of the suspended particles. The ringelectrode 10, having a certain initial potential with respect to thepreparation carrier 5, has the effect that particles, which are chargedwith a polarity opposite to the polarity of the electrodes and locatedin immediate proximity to the ionizing cartridge, are deposited not onthe ray-emitting preparation but on the said ring electrode. Such adeposit is facilitated, as known, by the field which is largelyheterogeneous adjacent the ionizing cartridge. The influence of adeposit on the ring electrode upon the remaining charging process can beneglected; at any rate it does not result into those disadvantages,which are produced by a deposit even of only filmy thickness on theemitting layer of the preparation. The provision of thedeposit-electrode 10 as a ring electrode surrounding the radiation conealso presents a disturbance or weakening of the ray emission, whichautomatically would take place if this electrode were formed e.g. by agrid arranged immediately in front of the preparation. Voltage issupplied by a high frequency transformer T which is connected with arectifier G, a condenser C, a resistance R and potentiometers R -R thefilter voltage being indicated as U In cases where due to larger housingsizes the sectional area of flow must be irradiated by a plurality ofpreparations disposed side by side, a separate ring electrode willsuitably be associated to each preparation. If the preparation is not ofcircular or square shape, but exists for instance in form of a strip,then the ring electrode 10,

instead of having an annular-shaped cross-section, may also be of ovalor elongate annular cross-section.

I claim:

1. An apparatus for electrically charging particles suspended in an aircurrent, said apparatus comprising a metal pipe, an at least partlyinsulating pipe constituting a continuation of said metal pipe and inalinement therewith, whereby an air current passes firstly through saidmetal pipe and then through said insulating pipe, a perforated electrodecarried by and extending transversely to the axial direction of saidmetal pipe, at least one grounded perforated counterelectrode carried byand extending transversely to the axial direction of said insulatingpipe, a conducting supporting plate located centrally within said metalpipe between said electrode and said counter-electrode and extendingtransversely to said metal pipe, a layer of at least one radioactivesubstance carried upon that surface of said supporting plate which facessaid counter-electrode, said radioactive layer emitting a radiation coneextending into the interior of said insulating pipe, saidcounter-electrode being located outside of said radiation cone, a ringelectrode located between said supporting plate and saidcounter-electrode adjacent to said supporting plate and extending in aplane perpendicular to the axial direction of said pipes, said ringelectrode surrounding said radiation cone, and a plurality of coaxialmetal tubes constituting the electrode system of "an electrostaticseparator and extending coaxially to the axial direction of said pipeson that side of the counter-electrode which is away from thefirst-mentioned electrode.

2. An apparatus in accordance with claim 1, comprising a direct currentsource supplying voltage to said conducting supporting plate, meansproducing a potential difference between said conducting supportingplate and said counter-electrode and means applying to said ringelectrode an initial voltage relatively to said supporting plate forprotecting said radioactive layer from being soiled by the deposition ofparticles.

OTHER REFERENCES Production of Unipolar Air with Radium Isotopes, by T.L. Martin, a reprint from Electrical Engineering, January 1954; 6 pages.

